The adaptation of the isoionic hemoglobin preparation developed in this Laboratory by the joint Forces Casualty Care Blood Resources Division based at Letterman Army Research Institute has provided stimulus to a renewed interest in several instruments developed in this laboratory. A modified oxygen binding to hemoglobin apparatus has been set up and is presently undergoing tests in the Laboratory of Molecular Biology, NIA. A highly modified cell is nearing completion of which will permit the measurement of the oxygen dissociation curve of hemoglobin simultaneously by a manometric method and spectroscopy. Such data are needed if the various models of how hemoglobin binds oxygen are to be critically tested. In collaboration with computational scientists at UCLA and DCRT a considerable effort has been mounted to have all of the needed programs operating on the local IBM AT rather than a main frame computer. The inertial drive quench flow apparatus and thermal-optical stopped flow apparatus have had a number of improvements made to them over the last year and it is expected that the quench flow machine will go operational in the laboratory of Biological Chemistry, NIA by the end of the summer. It has become clear that for the thermal stopped flow to be useful a differential version will need to be built and this should be finished in the next year. Experiments are planned on the ATPase ATP reactions of muscle as a test of the system.